1. Field of the Invention
The present invention relates to a switching module configured to handle transmission and reception of multiband communication signals, and wireless communication equipment including this switching module.
2. Description of the Related Art
Recent cellular phones facilitate phone calls and achieve high-speed communications of large-volume data by being configured to enable communications in a plurality of communication standards such as Global System for Mobile communications (GSM: Registered Trademark) standard, Wideband Code Division Multiple Access (W-CDMA) standard, Long Term Evolution (LTE) standard, and the like. In this case, a plurality of communication signals in different frequency bands is being transmitted through inside the cellular phone. Thus, in a conventional technology, as illustrated in FIG. 8, a switching module 100 capable of switching and connecting a common antenna 101 to one of a plurality of signal paths corresponding to the respective communication signals is proposed (Japanese Unexamined Patent Application Publication No. 2002-33714).
The switching module 100 is a module that handles transmission and reception of a communication signal in a 2.4 GHz band and transmission and reception of a communication signal in a 5 GHz band. The switching module 100 includes a 2.4 GHz band front end circuit 102a, a 5 GHz band front end circuit 102b, a bandpass filter 103 shared by both the front end circuits, and a switch 104 that selectively connects one of both the front end circuits 102a and 102b to the common antenna 101 and the bandpass filter 103.
Further, the 2.4 GHz band front end circuit 102a is composed of a voltage controlled oscillator (VCO) 105a for local oscillation, an up-converter mixer 106a1 for use at the time of transmission, a down-converter mixer 106a2 for use at the time of reception, a power amplifier 107a1 for transmission, a low noise amplifier 107a2 for reception, and a switch 108a for switching transmission and reception.
Similarly, the 5 GHz band front end circuit 102b is composed of a voltage controlled oscillator (VCO) 105b for local oscillation, an up-converter mixer 106b1 for use at the time of transmission, a down-converter mixer 106b2 for use at the time of reception, a power amplifier 107b1 for transmission, a low noise amplifier 107b2 for reception, and a switch 108b for switching transmission and reception.
However, in this kind of switching module, there are cases where, when a communication signal is inputted to a switch or a splitter (duplexer), harmonic emissions (for example, second-order harmonics or third-order harmonics) of the communication signal are generated as spurious emissions. In the switching module 100 that handles a plurality of communication signals in different frequency bands, there is a possibility that the harmonic components generated at the time of inputting a communication signal to the switch may interfere with another communication signal and degrade communication characteristics of the another communication signal. In view of this, the foregoing switching module 100 is provided with the switch 104 as well as the switches 108a and 108b that are separately provided for the respective front end circuits 102a and 102b. This separates the signal path of the 2.4 GHz band communication signal and the signal path of the 5 GHz band communication signal, and prevents mutual interference of the communication signals in both the bands.
However, in the conventional switching module 100, the switches 108a and 108b are provided for each pair of the front end circuits 102a and 102b, through which the communication signals in different frequency bands are being transmitted, respectively. This makes it difficult to meet the need of simplification and downsizing of switching modules associated with recent downsizing of cellular phones. To simplify and downsize switching modules, it is possible to configure the switch portions 104, 108a, and 108b provided for the different bands using a single IC. However, in such a configuration, the switch portions 104, 108a, and 108b that switch and connect the communication signals in different frequency bands are arranged in close proximity to each other. Further, all the switch portions 104, 108a, and 108b are connected to a common antenna terminal within the IC. Thus, harmonic components generated at one of the switch portions are likely to leak to another switch portion or the signal path connected to that switch portion, and the interference may occur between different bands.
Further, some cellular phones in recent years are provided with an antenna for a different communication system such as, for example, a global positioning system (GPS), a GSM, and the like. In such a case, harmonics of an 850 MHz band signal in GSM may overlap the frequency of GPS signal in some cases, and the reception sensitivity of GPS may degrade if such harmonics are inputted via an antenna for GPS.
Further, in the case where a plurality of switches is included in a single switch IC, redesigning of the switch IC may be required every time the design of a switching module is changed. This increases the manufacturing cost.